In order to facilitate access to fields by heavy agricultural machinery during the spring and fall seasons, the ground of these fields is usually drained by an underground system. One widely used method consist in disposing drainage pipes made of plastic or other suitable material in the ground according to specific patterns. These pipes are usually buried at a depth of approximately 0,9 to 2 meters with a tilt angle between 0.01% and 2% and are spaced 10 to 50 meters apart.
When the flow of water in the drainage pipes is not controlled, it varies mainly as a function of the height of water directly above the pipes. Therefore, if the flow is not controlled after a given precipitation, the drainage system will evacuate water in the ground until the level of underground water reaches the level of the drainage pipes.
Many studies have shown that uncontrolled drainage systems cause dehydration of the soil during the crucial growing periods if no sufficient replenishment is provided by precipitations, such as rain. Indeed, since pipes are buried at a level lower than the level of water necessary for optimal plant (or crop) growth and since they drain the soil until the level of water is approximately equal to their level of burial, they are often prejudicial to such growth.
Numerous examples of drainage and/or irrigation control systems designed to overcome the above-mentioned problems exist. Some of them are found described in Canadian Pat. No. 1,088,330 and U.S. Pat. Nos. 4,621,945, 3,559,408 and 3,368,355. Some most Widely used control chambers are shown in U.S. Pat. Nos. 4,621,945 and 3,368,355.
However, these types of control chambers, while limiting the risks of excessive drainage, create a risk of underdrainage. Control chambers are usually adapted to drainage systems and are designed by taking into consideration fixed parameters, such as the hydraulic conductivity of the soil, the drainage coefficient, etc. When added to existing systems, the control chambers, whether of the "overflow" or "float" type, create a virtual drainage depth which is higher than the depth for which the system is designed. This situation can lead to the deterioration of crop since most roots are vulnerable to deprivation of oxygen by excessive water accumulation.